Structural protection system for buildings

ABSTRACT

A structural protection system of buildings is described, comprising at least one bearing structure ( 2 ) connected with at least one wall of said building (E). The bearing structure ( 2 ) is rigidly connected to the wall of the building (E) and the bearing structure ( 2 ) is a specialized structure comprising an energy dissipation device ( 1 ) adapted to dissipate the energy generated by the oscillations of the bearing structure due to earth tremor.

The present patent application for industrial invention relates to astructural system for seismic protection of buildings. The structuralsystem according to the invention is especially suitable for seismicprotection of existing buildings, with special reference to buildingsthat play an important social role, classified as strategic buildings(hospitals, schools, barracks, etc.) and also of new buildings.

FIG. 1 illustrates a structural system for seismic protection ofbuildings according to the prior art.

A plurality of dissipation devices (1) are installed in building (E) tobe protected, being designed to dissipate the energy generated by theoscillations of the building due to earth tremor. According to thedifferent techniques, said dissipation devices (1) are installed insidethe building (E) or outside it on the walls.

The building (E) comprises a framework of the bearing structure. Byframework we mean a frame composed of multiple floors (S) and verticalelements (P), such as pillars or bearing walls, in order to generate aplurality of spaces (M).

At least one dissipation device (1) is installed in each space (M) ofsaid framework, in bracing configuration, preferably with diagonaldirection with respect to the space (M).

Each dissipation device comprises a dissipation means (1 c) disposedbetween two rigid rods.

A first end (1 a) of the first rod of the dissipation device is tied toa portion of angle between the lower floor (S) of the space and a firstlateral wall of the building.

A second end (1 a) of the second rod of the dissipation device is tiedto a portion of angle between the upper floor (S) of the space and asecond intermediate wall of the building.

Therefore each dissipation device (1) works autonomously and contributesto compensate wall deformations of each space (M) of the framework.

Such a structural system is impaired by a series of drawbacks due to thefact that the dissipation devices (1) must be disposed inside thebuilding.

JP 09 235890 (Kajima Corp.) discloses a reinforcement andvibration-damping structure for existing buildings.

The purpose of the present invention is to eliminate the drawbacks ofthe prior art by disclosing a structural system that is able to opposethe oscillations of buildings due to earth tremor in an efficient andefficacious way.

Another purpose of the present invention is to provide such a structuralsystem for seismic protection of buildings that is versatile and at thesame time easy to make, install and maintain.

These purposes are achieved according to the present invention with thefeatures claimed in independent claim 1.

Advantageous embodiments are disclosed in the dependent claims.

According to the invention the building to be seismically protected iscombined with a specialized structure designed to oppose seismic actionsby dissipating energy.

In case of existing buildings, the specialized structures can be simplyinstalled in external position, without having to carry out any worksinside the building.

The specialized structure can consist in a tower or frame or column withsuitably rigidity, connected to the building by means of rigid rods withtwo hinges normally disposed at each floor level.

Hereinafter, for the sake of simplicity, reference will be always madeto a specialized structure that consists in a tower.

The tower is tied at the base with a spherical joint or hinge.Therefore, the tower is free to oscillate in any direction around thespherical joint, rotating and pivoting on the joint (centre ofrotation).

Dissipation devices or dampers are applied around the base of the tower,which strongly oppose the rotation and oscillation of the tower, thussuffering movements and dissipating energy by means of hysteresiscycles.

To amplify displacements (travel: elongation and shortening) of thedissipation devices, suitable mechanisms that operate by means of crankgears can be provided.

The global dissipation system, which is concentrated at the base of thetower, can be of any type.

Therefore, the main function of the tower is to oppose the effectsproduced by earth tremor by dissipating energy in the specialized areawhere dissipation devices of generic type (dampers) are installed.

The re-centering (balancing) of the tower is guaranteed by theelasticity of the building structure and also by elastic elements thatcan be connected in parallel to the energy dissipation means.

In new buildings the tower that acts as seismic-resistant-dissipationelement can be inserted inside the building (for example in thestairwell-elevator area). The structural system of the invention hasseveral advantages compared to the known systems.

Considerable cost reduction is obtained compared to traditional systemsthat are made inside the buildings and require additional works inaddition to structural works.

If the external seismic-resistant-dissipation structure is of spatialtype (tower), it can provide additional usable volume (enlargement), nolonger being an end in itself (of structural type only) and with lowerincidence of the seismic adaptation cost.

Such a seismic-resistant-dissipation structure can be, for example, avertical connection element (stairs, elevator) or emergency staircase.Reference is made to the frequent installation of steel emergencystaircases outside public buildings, which can also represent a seismicprotection element if designed with the structural system of theinvention.

Maintenance of dissipation devices can be carried out withoutinterrupting the use of the building during maintenance works,consequently reducing the costs caused by the temporary lack of use.

The installation of the specialized structure can be carried out withoutinterrupting the ordinary use of the building to be protected.

Dissipation devices are concentrated in a single specialized area withlimited dimensions (tower base), which is consequently easy to inspectand maintain. For very high buildings the specialized dissipation areacan be also positioned at higher levels, not only at the base of thetower.

The dissipation system of the invention guarantees high efficiency,taking full advantage of the devices, and high efficacy of theseismic-resistant devices that are concentrated in a single specializedarea compared to the known methods with devices disseminated on thebuilding, the operation of which is affected by the uncertain seismicreaction of the building as a whole, especially due to the presence ofnon-structural elements (walls in general, etc.).

The rigidity of external seismic-resistant structures with verticaldevelopment (tower, frame, column) connected by means of rigid rods tothe building is such that it regularizes the deformation (horizontalfloor displacements) of the building that is subject to earth tremor,which is generally irregular.

Complete reversibility of the system is guaranteed because noalterations are made to the building, as in case of internal works.

In case of hospital or school buildings, if the structural system of theinvention has been correctly studied from an architectural viewpoint, itcan provide improved design and improved operation with the use ofadditional structures (new spaces, services, etc.). This is madepossible also because of the high formal flexibility of additionalstructures (for example, the tower can have a square, rectangular,polygonal, circular, etc. shape, can have a constant height or can betapered vertically).

Additional characteristics of the invention will appear evident from thedetailed description below, which refers to merely illustrative, notlimiting embodiments, illustrated in the enclosed drawings, wherein:

FIG. 1 is a diagrammatic cross-sectional view along a vertical planethat shows a structural system for seismic protection of buildingsaccording to the prior art;

FIG. 2 is a diagrammatic cross-sectional view along a vertical planethat shows a first embodiment of the structural system for seismicprotection of buildings according to the present invention that providesfor a specialized structure with distributed energy dissipation system;

FIG. 3 is the same view as FIG. 2, except for it shows a secondembodiment of the structural system of the invention with specializedstructure with energy dissipation system concentrated at the base;

FIG. 4 is a plan view of the structural system of FIG. 3;

FIG. 5 is a perspective view of the structural system of FIG. 3;

FIG. 6 is the same view as FIG. 3, except for it shows a differentversion of the energy dissipation system of FIG. 3, which provides for alever mechanism that multiplies the travel of the energy dissipationdevice;

FIG. 6A is an enlarged view of the detail contained in circle (A) ofFIG. 6.

FIG. 7 is the same view as FIG. 6, except for it shows the oscillationof the structural system of FIG. 6 during earth tremor;

FIG. 7A is an enlarged view of the details contained in circles (A) and(A′) of FIG. 7;

FIGS. 8 and 9 are two side elevation views that show a different versionof the structural system of the invention, wherein the specializedstructure consists in a planar frame;

FIG. 10 is a plan view of the structural systems of FIGS. 8 and 9;

FIG. 11 is a cross-sectional view along a vertical plane that shows thespecialized structure disposed as nucleus inside the building;

FIGS. 12 and 12A are two side elevation views that show a differentversion of the structural system of the invention, wherein thespecialized structure consists in a column;

FIG. 13 is a plan view of the structural system of FIG. 12; and

FIG. 14 is a perspective view of the structural system of FIG. 12.

Now referring to FIG. 2 a first embodiment of the structural system forseismic protection of buildings according to the present invention isdisclosed.

The building (E) to be protected comprises a plurality of levels definedby floors (S) disposed according to horizontal planes. The structuralsystem of the invention comprises at least one bearing structure (2)rigidly connected to the building (E).

The bearing structure (2) has basically the same height as the building(E) and is rigidly connected to the building by means of a plurality ofrigid rods (3). The rod (3) is provided with a first end (3 a) tied to awall of the building (E) and a second end (3 b) tied to the bearingstructure (2).

Advantageously, the bearing structure (2) is provided with a pluralityof horizontal reinforcement elements (S′) disposed at the same height asthe floors (S) of the building (E). Advantageously, the rigid rods (3)are disposed according to horizontal straight lines on the floors (S) ofthe building and the corresponding reinforcement elements (S′) of thebearing structure.

The bearing structure (2) is a specialized structure that comprises anenergy dissipation system adapted to dissipate the energy of theoscillations suffered by the bearing structure (2) due to earth tremor.

It must be noted that the specialized structure (2) is rigidly connectedto the building (E). Therefore the energy dissipation system of thespecialized structure is able to compensate and damp also theoscillations suffered by the building (E) during the shocks.

According to the embodiment of FIG. 2, the specialized structure (2) isa tower disposed outside the building (E) and the horizontalreinforcement elements are floors (S′) of the tower disposed between afirst vertical wall (2 a) facing the building (E) and a second verticalwall (2 b) opposite the first vertical wall (2 a). In this way avertical row of parallelepiped spaces (V) is defined in the tower (2).

One dissipation device (1) is disposed in each space (V) of the tower(2), in bracing configuration, diagonally, in such a way to generate anenergy dissipation system of the specialized structure (2) distributedalong the entire height of the specialized structure.

The dissipation device comprises an energy dissipation means (1 c)disposed between two rigid rods. The energy dissipation means (1 c) canbe, for example, a chamber with fluid. A shock-absorbing element, suchas elastic means, spring means or damper can be disposed in parallelposition to the energy dissipation means (1 c).

In each space (V) the dissipation device (1) comprises:

-   -   a first end (1 a) tied to a portion of angle between the lower        floor (S′) of the space (V) and the first lateral wall (2 a) of        the tower, and    -   a second end (1 a) tied to a portion of angle between the upper        floor (S′) of the space (V) and the second lateral wall (2 a) of        the tower.

In the following description identical elements or elementscorresponding to elements that have already been described are indicatedwith the same reference numerals, omitting their detailed description.

FIGS. 3-5 describe a second embodiment of the structural system of theinvention, wherein the dissipation system is concentrated at the base ofthe tower (2).

In such a case, the base of the tower (2) is tied to a spherical jointor hinge (4) mounted on a base (B) fixed to the ground. The verticalaxis of the tower (2) passes through the centre of the spherical joint(4).

A plurality of dissipation devices (1) is disposed in peripheralposition around the spherical joint (4). Each dissipation device (1) isprovided with a first end (1 a) tied to the base (B) and a second end (1b) tied at the base of the tower. Advantageously, the tower (2) has abase (20) shaped as overturned pyramid, wherein the vertex of thepyramid is tied to the spherical joint (4).

As shown in FIG. 4, to protect the rectangular building (E), twospecialized structures (2) are sufficient, being disposed in the longopposite sides of the building, near the opposite angles of thebuilding.

The connection system of the tower (2) to the building (E) comprisesfour rigid rods (3) in each floor, disposed in W-configuration withthree connection hinges (3 a) on the building (E) and two connectionhinges (3 b) on the tower.

As shown in FIG. 5, each tower (2) is damped by eight dissipationdevices (1) disposed at the four angles of the tower base and along thecentral lines of the four sides of the tower base.

Referring to FIGS. 6, 6A, 7 and 7A, a different version of the energydissipation system is described.

As shown in FIG. 6A, according to this version, each dissipation device(1) is connected to a lever mechanism (5) to multiply the travel of thedissipation device (1), i.e. elongation/shortening of the dissipationdevice (1) to compensate the oscillation of the tower (2).

The lever mechanism (5) comprises two levers (L1, L2). The first lever(L1) is pivoted in the central point (F1) to a projection (51) of aflange (50) tied to the base (B). The second lever (L2) has a first end(La) pivoted at a projection of a flange (52) tied to the base (20) ofthe tower and a second end (Lb) pivoted at one end of the first lever(L1).

The dissipation device (1) has a first end (1 a) pivoted at a projectionof the flange (52) tied to the base (20) of the tower and a second end(1 b) pivoted at the other end of the first lever (L1).

In idle state the dissipation device (1) is basically as long as thesecond lever (L2) and parallel to the second lever (L2) in such a waythat first lever (L1), second lever (L2), flange (52) and dissipationdevice (1) form an articulated quadrilateral that can oscillate aroundthe fulcrum (F1).

Referring to FIGS. 7 and 7A, when the building (E) suffers oscillationdue to earth tremor, also the tower (2) that is rigidly tied to thebuilding (E) suffers oscillation with horizontal displacement (δ_(o)) ofthe top of the tower. Consequently, the base (20) of the tower suffers avertical displacement (δ_(v)) that must be damped and compensated by thedissipation devices (1).

If Li is the length of the dissipation device in idle state and Lf isthe length of the dissipation device after compression or elongation dueto oscillation of the tower, the travel of the dissipation device isdetermined by the relationship:

δ_(D) =|Li−Lf|

The travel (δ_(D)) of the dissipation device is related to the levermechanism (5) and vertical displacement (δ_(v)) of the tower base.

(b1) is the distance between the fulcrum (F1) of the first lever (L1)and the fulcrum (Lb) of the second lever (L2) with the first lever (L1).(b2) is the distance between the fulcrum (F1) of the first lever (L1)and the fulcrum (1Lb) of the dissipation device (1) with the first lever(L1).

As shown in FIG. 7A, the travel of the dissipation device is determinedby the relationship:

δ_(D) =|Li−Lf|=δ _(V)*(1+b2/b1)

If the fulcrum (F1) is in the centre of the first lever (L1), i.e.(b1=b2), the travel of the dissipation device is:

δ_(D)=2*δ_(V)

The elongation or shortening of the dissipation device (1) will be twiceas the vertical displacement (δ_(V)) of the base (20) of the tower.

Referring to FIGS. 8, 9 and 10, a different version of the structuralsystem of the invention is disclosed, wherein the specialized structureis a planar frame (102) composed, for example, of a reticular framework.

Also in this case, the dissipation devices (1) can be disposed at thebase of the frame (102). The frame (102) is tied to the ground by meansof a planar hinge (104) instead of a spherical joint.

As shown in FIG. 10, to protect a rectangular building, four frameworks(102) are necessary, being disposed in the four sides of the building.

FIGS. 3, 5, 6, 7, 8 and 9 show five-story buildings and specializedstructures (2; 102) provided with energy dissipation system concentratedonly at the base of the structure.

However, in case of taller buildings, each specialized structure can bemade of multiple overlapped parts that are mutually tied by means of acentral hinge around which the dissipation devices are disposed. Theconnection between the various parts of the bearing structure is exactlymade as the connection of the base of the bearing structure to theground.

Referring to FIG. 11, if a new building (E) is built, the specializedstructure (202) can be the nucleus of the building, that is to say atower inside the building that is rigidly connected to the internalwalls of the building.

In such a case, the tower (202) is provided with a specialized energydissipation system, such as the systems described in the aforementionedembodiments.

Referring to FIGS. 12 12A, 13 and 14, a different version of thestructural system of the invention is described, wherein the specializedstructure is a column (302).

Also in this case, the dissipation devices (1) can be disposed at thebase of the column (302). The column (302) is anchored to the ground bymeans of a spherical joint (4).

FIG. 12 A shows an embodiment of the present invention in which the baseof the column (302) is a horizontal plane under which the dissipationdevices (1) and relevant multiplier lever mechanisms (5) are mounted.

As shown in FIGS. 13 and 14, to protect a rectangular building, fivecolumns (302) are necessary, being disposed in a row on the two longsides of the building. The columns (302) are mutually connected by meansof rigid rods (303).

Numerous variations and modifications can be made to the presentembodiments of the invention by an expert of the field, while stillfalling within the scope of the invention as claimed in the enclosedclaims.

1. Structural protection system of buildings comprising at least onebearing structure connected with at least one wall of said building,wherein said bearing structure is rigidly connected with the wall ofsaid building, and said bearing structure is a specialized structurecomprising an energy dissipation system adapted to dissipate the energygenerated by the oscillations of the bearing structure due to earthtremor, characterized in that the bearing structure has a base and saidenergy dissipation system is arranged between the ground and the base ofsaid bearing structure, the base of the bearing structure being tied tothe ground by means of at least one spherical joint or hinge; whereinsaid spherical joint or hinge is arranged on the vertical axis of thebearing structure and said energy dissipation devices are arranged inperipheral position with respect to said spherical joint or hinge. 2.Structural system as claimed in claim 1, wherein said bearing structureis rigidly connected to the wall of said building by means of rigid rodshaving a first end connected to the wall of the building and a secondend connected to said bearing structure.
 3. Structural system as claimedin claim 2, wherein that said rigid rods are arranged according tohorizontal planes in correspondence with the floors of the building andthe bearing structure provides for reinforcement elements arrangedaccording to horizontal planes in correspondence with the floors of saidbuilding.
 4. Structural system as claimed in claim 1, wherein the energydissipation system is composed of a plurality of energy dissipationdevices comprising an energy dissipation means arranged between tworigid rods.
 5. Structural system as claimed in claim 4, wherein saidenergy dissipation device comprises a shock-absorbing element arrangedin parallel position with respect to the energy dissipation means. 6.Structural system as claimed in claim 1, wherein said energy dissipationdevices have a first end tied to the ground and a second end tied to thebase of said bearing structure.
 7. Structural system as claimed in claim1, wherein said energy dissipation system comprises a lever mechanismadapted to multiply the travel of said energy dissipation devices duringthe oscillation of the bearing structure.
 8. Structural system asclaimed in claim 7, wherein said lever mechanism comprises a first leverpivoted at a flange tied to the ground and a second lever having an endpivoted at the base of the bearing structure and a second end pivoted atthe first lever, in which the energy dissipation device has a first endpivoted at the base of the bearing structure and a second end pivoted atthe first lever.
 9. Structural system as claimed in claim 1, wherein thebearing structure is a tower external to the building.
 10. Structuralsystem as claimed in claim 1, characterized in that the bearingstructure is a planar frame external to the building.
 11. Structuralsystem as claimed in claim 1, wherein the bearing structure is a towersituated inside the building.
 12. Structural system as claimed in claim1, wherein the bearing structure is a column.
 13. Structural system asclaimed in claim 1, wherein said bearing structure is composed ofmultiple overlapped parts tied by a central hinge around which saidenergy dissipation devices are arranged.